Suppose I am using DFDL to parse email headers.  Suppose the RFC only allows 3 headers:  To, From, Subject.  DFDL can handle this, no problem.

But suppose I get an email that includes a 4th header, one I have not planned for (i.e., have not included in the DFDL schema), don’t care about, and don’t want in the infoset.  Like so:

From: <john@doe.com>

To: <jane@doe.com>

Keywords:  sales                       <-- this line should be ignored!

Subject:  Latest sales figures

Can DFDL handle this?  Does it have a mechanism for allowing me to ignore (and thus drop) data I haven’t planned for and don’t care about?